December weather forecastMillbrae, CA
December
Weather in December
December, the first month of the winter in Millbrae, is also a moderate month, with an average temperature ranging between max 55.6°F (13.1°C) and min 47.8°F (8.8°C).Temperature
The coldest period is December, when temperatures fluctuate between an average high of 55.6°F (13.1°C) and a low of 47.8°F (8.8°C).Humidity
The average relative humidity in December is 72%.Rainfall
In Millbrae, California, during December, the rain falls for 11.1 days and regularly aggregates up to 2.17" (55mm) of precipitation. Throughout the year, there are 81.5 rainfall days, and 12.8" (325mm) of precipitation is accumulated.Daylight
With an average of 9h and 36min of daylight, December has the shortest days of the year.On the first day of December, sunrise is at 7:06 am and sunset at 4:51 pm. On the last day of the month, sunrise is at 7:24 am and sunset at 5:01 pm PST.
Sunshine
With an average of 5.8h of sunshine, December has the least sunshine of the year.UV index
The months with the lowest UV index are February and December, with an average maximum UV index of 3. A UV Index estimate of 3 to 5 represents a moderate threat to health from exposure to the Sun's UV radiation for ordinary individuals.Note: In December, an average UV index of 3 transforms into the following instructions:
Be mindful. Individuals with a lighter skin tone may suffer burns in less than 30 minutes. The Sun is most powerful around mid-day, so it's a good practice to reduce direct exposure. On sunny days, it's ideal to wear sunglasses that filter out UVA and UVB rays.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in December
Millbrae, CA
- Average high temperature in December: 55.6°F
The warmest month (with the highest average high temperature) is September (70.2°F).
The month with the lowest average high temperature is December (55.6°F).
- Average low temperature in December: 47.8°F
The month with the highest average low temperature is September (56.8°F).
The coldest month (with the lowest average low temperature) is January (47.5°F).
Average pressure in December
Millbrae, CA
- Average pressure in December: 30.11"Hg
The month with the highest atmospheric pressure is January (30.13"Hg).
The month with the lowest atmospheric pressure is September (29.92"Hg).
Average wind speed in December
Millbrae, CA
- Average wind speed in December: 7.2mph
The windiest month (with the highest average wind speed) is April (8.3mph).
The calmest month (with the lowest average wind speed) is September (6.1mph).
Average humidity in December
Millbrae, CA
- Average humidity in December: 72%
The month with the highest relative humidity is August (78%).
The month with the lowest relative humidity is October (70%).
Average rainfall in December
Millbrae, CA
- Average rainfall in December: 2.17"
The wettest month (with the highest rainfall) is February (2.44").
The driest month (with the least rainfall) is July (0.08").
Average rainfall days in December
Millbrae, CA
- Average rainfall days in December: 11.1 days
The month with the highest number of rainy days is March (12.8 days).
The months with the least rainy days are June and July (2.4 days).
Average daylight in December /
Average sunshine in December
Millbrae, CA
- Average daylight in December: 9h and 36min
The month with the longest days is June (Average daylight: 14h and 42min).
The month with the shortest days is December (Average daylight: 9h and 36min).
- Average sunshine in December: 5h and 48min
The month with the most sunshine is July (Average sunshine: 11h and 48min).
The month with the least sunshine is December (Average sunshine: 5h and 48min).
Average sunshine days in December
Millbrae, CA
- Average sunshine days in December: 19.1 days
The month with the most sunshine days is July (24.6 days).
The month with the least sunshine days is March (16.3 days).
Average UV index in December
Millbrae, CA
- Average UV index in December: 3
The months with the highest UV index are June, July, August and September (UV index 5).
The months with the lowest UV index are February and December (UV index 3).
Average cloud cover in December
Millbrae, CA
- Average cloud cover in December: 35
The month with the most cloud cover is March (Cloud cover 36).
The months with the least cloud cover are July and September (Cloud cover 15).
Average visibility in December
Millbrae, CA
- Average visibility in December: 6mi
The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
